If America is a nation of immigrants, it's also a nation of immigrants' husbands, wives, parents and children - and their brothers, sisters, nieces and nephews too.

That could begin to change under legislation being written in the Senate, where the nation's longstanding emphasis on family-based immigration is coming under scrutiny.

Unlike most other industrialized nations, the U.S. awards a much larger proportion of permanent residency status to family members of U.S. citizens and permanent residents than to foreigners with job prospects here. About two-thirds of permanent legal immigration to the U.S. is family-based, compared with about 15 percent that is employment-based, according to the Migration Policy Institute. The remainder is largely humanitarian.

It's a lopsided ratio that may change under a bill being crafted by a Senate bipartisan negotiating group that is aiming to release legislation next month. Several senators involved in the talks said employment-based immigration must increase to help American competitiveness and the U.S. economy. High-tech companies have been pleading for more workers, and some Republicans, in particular, believe the educational backgrounds and employment potential of prospective immigrants should be a bigger part of the calculus in awarding green cards, the permanent resident visas that are the key step toward citizenship.

"In the 21st century, more of our immigration needs to be based on merit and skill,'' said Republican Sen. Marco Rubio of Florida, a member of the "Gang of Eight'' senators negotiating an immigration bill.The senators' proposals are still evolving and details remain unclear. For advocates of family-based immigration, the key question has become whether the increased focus on employment-based immigration will come in addition to the family-based system or to its detriment.

"Family unity has been the cornerstone of our immigration system for decades and should remain so,'' said Kevin Appleby, director of migration policy at the U.S. Conference of Catholic Bishops.

"We're concerned that the family-based system is vulnerable and that visas could be taken away or categories could be eliminated, and we would strongly oppose that.''Under current law, U.S. citizens can petition to bring their spouses, parents and minor unmarried children into the country without any limit on the number coming in. There are caps on all other categories, including petitions for citizens' adult or married children, citizens' brothers and sisters and their children and the immediate family members of legal permanent residents.

The law also caps the percentage of immigrants that can come from any one